The present invention relates to devices for eliminating the phenomena of acoustic resonance inside a cavity and relates in particular to an aircraft turbomachine comprising a deflector which is arranged in a fan conduit in order to eliminate such phenomena in the air passage of an exchanger.
A dual-flow turbomachine generally comprises an air intake system in order to provide air to the air consuming systems of the aircraft such as, for example, the system for renewal and regulation of the air pressure in the cabin or de-icing systems. The air intake system takes in warm air in the region of the hot portions of the turbomachine and cold air in the region of the fan conduit of the turbomachine. So that the temperature of the air supplied to the aircraft air systems remains within acceptable limits, the air intake system comprises an exchanger (PCE) in which the flows of cold and hot air intersect. The cold air is conveyed to the exchanger via an air passage which connects the exchanger to the fan conduit in a fluidic manner. The passage comprises an air inlet opening at the upstream end thereof and a valve of the butterfly type which is located at the downstream end thereof, in the region of the exchanger. The opening angle of the butterfly valve is controlled in accordance with the air requirements of the consumer systems.
The inlet opening is level with the wall of the fan conduit in order to reduce the aerodynamic impact thereof, in particular the drag thereof. With such a geometry, however, when the butterfly valve is closed or almost closed, a shear flow layer which extends through the opening and which is level with the wall of the fan conduit is formed. The interaction of the shear flow layer with a downstream inlet edge of the inlet opening creates acoustic waves which propagate and are amplified in the passage between the valve and the shear layer. Some of these waves have frequencies which are close to the resonance frequency of the passage which may bring about acoustic resonance phenomena of the cavity.